Comparative examination of the physical parameters of the sol gel produced compounds La0.5Ag0.1Ca0.4MnO3 and La0.6Ca0.3Ag0.1MnO3

摘要

In this paper, the physical characteristics of La0.5Ag0.1Ca0.4MnO3 and La0.6Ca0.3Ag0.1MnO3 compounds have been studied. Structural analysis by XRD showed that both samples crystallize in an orthorhombic structure. For the La0.5Ag0.1Ca0.4MnO3 sample it can be seen that there are two bands: the first is due to the stretching Mn-O bond the v(s) vibration mode, relates to the internal motion of a length-changing Mn-O, whereas the second corresponds to the v(b) bonding mode, which is sensitive to a change in the Mn-O-Mn angle. For the compound La0.6Ca0.3Ag0.1MnO3 the v(b) band is absent. The magnetic measurements show that the two compounds have a single transition from the PM state to the FM state with an increase in the Curie transition temperature T-c, for the compound La0.6Ca0.3Ag0.1MnO3. Similarly, the substitution of silver in calcium increases the value of the magnetization at low temperature. We also studied the magnetocaloric effect of our compounds. This study shows a significant change in magnetic entropy Delta S-M that took place around their magnetic transition temperatures T-c. Under the influence of a 5 T magnetic field. The largest fluctuation in magnetic entropy is in the order of - 8.67 J/kg.K for the compound La0.6Ca0.3Ag0.1MnO3 this value is considered significant. The magnetocaloric results indicate that the compound La0.6Ca0.3Ag0.1MnO3 is the best sample which has a large RCP which suggests its good candidate in the field of magnetic cold. Based on the Banarjee criterion and Landau theory, a second-order transition is observed for both samples in the vicinity of the Curie transition T-c. The experimentally obtained value of Delta S(M )is smaller than the theoretically calculated one, which proves that the transition is an unconventional transition even under the influence of a 5 T magnetic field.